2 February 2017 | Rho Oph

The Rho Ophiuchi Cloud Complex (Rho Oph for short, or the Ophiuchus Molecular Cloud and named after a bright star in the region) is a dark nebula, an emission and reflection nebula of about 14 light-years across that is located some 460 light-years away from Earth in the constellation of Ophiuchus (the Serpent-bearer). It is one of the closest star-forming regions to the Solar System.

It consists of two major regions of dense gas and dust. Lynds 1688 (L1688), the bright white main cloud of molecular hydrogen, a key molecule allowing new stars to form from cold cosmic gas, with two long filaments trailing off in different directions. The other, Lynds 1689 (L1688), has a star-forming region with one long filament.

Temperatures of the clouds range from minus 260 degrees Celsius to minus 251 degrees Celsius, and there is a total of about 3,000 times the mass of the Sun in material. Over half of the mass of the complex is concentrated around the bright Lynds 1688 cloud, and this is the most active star-forming region.

The first brown dwarf to be identified in a star-forming region was Rho Oph J162349.8-242601, located in the Rho Ophiuchi Cloud Complex. One of the older objects at the edge of the primary star-forming region was found to be a circumstellar disk seen nearly edge on. It spans a diameter of 300 AU and contains at least twice the mass of Jupiter. The million-year-old star at the center of the disk has a temperature of 3,000 Kelvin and is emitting 0.4 times the luminosity of our Sun.

Rho Oph can be found rising above the plane of the Milky Way in the night sky, bordering the constellations Ophiuchus and Scorpius, 1° south of the star ρ Ophiuchi.